I think you want to go into this meeting with the expectation that you are there to continue to build the existing relationship you have and that you would like to gain any tips or tricks he might have as you are launching your business. Maybe the ask in this situation is around if he can be a referral for you when you met the right client or maybe you ask if his team could to give your software a try for a few months for more feedback. I wouldn't try to sell this guy quite yet. Let it happen organically as a result of him trusting you and trying to help you.